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(e)
The landing gear continues to retract and the door continues to open until the landing gear is up and latched in the uplock assembly. Then, the uplock-operated sequence valve again sends fluid to the door actuator. The door actuator retracts to close the door until the actuator locks the door closed.
(f)
When the door is fully closed and locked, the control lever is moved to OFF. This changes the position of the selector valve to prevent the supply of hydraulic pressure to the landing gear system. The hydraulic lines are opened to return, which completes the retraction cycle.
(2)
Landing Gear Extension
(a)
The extension cycle starts with the landing gear up and locked and the main landing gear door closed and locked. With the control lever in DN, hydraulic fluid flows through the selector valve to pressurize the hydraulic lines for landing gear extension.
(b)
Hydraulic fluid flows through the truck positioner shuttle valve to the truck positioner actuator. The actuator is pressurized to hold the truck at an angle as it moves out of the wheel well.
(c)
Hydraulic fluid flows through the uplock-operated and downlock-operated sequence valves to the door actuator. The mechanical lock in the door actuator is released and the actuator extends to open the main landing gear door. Hydraulic fluid also flows to the downlock actuator which applies pressure to extend the actuator and lock the downlock links. But, at this time, the links cannot move since the landing gear is still locked.
(d)
When the door is approximately 90 percent open, the door-operated sequence valve sends hydraulic fluid to the uplock actuator. The uplock actuator retracts to move the uplock hook from the latched position. This releases the landing gear from the uplock assembly.
(e)
When the door is approximately 95 percent open, the door-operated sequence valve sends hydraulic fluid to the retract actuator. The retract actuator extends to lower the landing gear.
(f)
The door opens fully. The landing gear continues to lower until it is down and the pressure applied to the downlock actuator extends the actuator to move the downlock links overcenter to the locked position. Then, the downlock-operated sequence valve again sends hydraulic fluid to the door actuator. The door actuator retracts to close the door until the actuator locks the door closed.
(g)
When the door is fully closed and locked, the extension cycle is complete.
B.
Control
(1)
The extension and retraction system for the main landing gear is controlled by the landing gear control system (AMM 32-31-00/001).
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MAIN GEAR EXTENSION AND RETRACTION - ADJUSTMENT/TEST
____________________________________________________
1. General_______
A. This test is used to make sure that main gear extension and retraction operates satisfactorily. In this test, however, the nose gear is also cycled. This test does not contain the data for a complete landing gear extension and retraction system test or any adjustments.
TASK 32-32-00-705-003
2. Operational Test - Main Landing Gear Extension and Retraction_____________________________________________________________
A. Equipment
(1)
Stop Watch
B.
References
(1)
AMM 07-11-01/201, Jacking Airplane
(2)
AMM 24-22-00/201, Electrical Power - Control
(3)
AMM 29-11-00/201, Pressurize/Depressurize Main Hydraulic System
(4)
AMM 32-00-15/201, Landing Gear Door Locks
(5)
AMM 32-00-20/201, Landing Gear Downlocks
C.
Access
(1)
Location Zones
212 Control Cabin (Right)
730 Main Landing Gear and Doors (Left)
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本文链接地址：757 AMM 飞机维护手册 起落架 CHAPTER 32 - LANDING GEAR 2(43)
